In the generation of Sjögren’s syndrome (SS), CD4 positive αβ T cells have a crucial role. Previous studies have provided evidence about the T cell receptor (TCR) Vβ and Vα genes on these T cells, and sequence analysis of the CDR3 region indicates the presence of some conserved amino acid motifs, supporting the notion that infiltrating T cells recognise relatively few epitopes on autoantigens.¹

Candidate autoantigens recognised by T cells that infiltrate the labial salivary glands of patients with SS have been analysed, and Ro/SSA 52 kDa,² α-amylase, heat shock protein, and TCR BV6 have been identified, although Ro/SSA 52 kDa reactive T cells were not increased in peripheral blood.³ Gordon et al indicated that anti-M3R autoantibodies occurred in SS and were associated with the sicca symptoms.⁴ Recently, we provided evidence for the presence of autoantibodies against the second extracellular domain of muscarinic acetylcholine receptor (M3R) in a subgroup of patients with SS.⁵ The M3R is an interesting molecule, because this portion has an important role in intracellular signalling,⁵ although the function of anti-M3R autoantibodies remains unknown.

The mechanism through which a peptide is recognised by a TCR is flexible. If the amino acid residue of the peptide ligands for TCR is substituted by a different amino acid and can still …